1. Field of the Invention
The present invention relates to antimicrobial powders which comprise an antimicrobial metal supported on the surface of hydrous titanium oxide or titanium oxide particles and a method for making them.
2. Description of the Related Art
It is well known that metals such as copper and silver have antimicrobial properties as so-called oligodynamic action. For example, there have been proposed uses of such metals in therapeutic or preventive medicines which use copper ion generated from various soluble copper salts, copper complex compounds, etc.. Uses of such metals are also made in bactericidal filters, algicidal filter, algicidal net, bactericidal and deodorant cloths or leathers employing superfine copper fibers produced from copper metal. Specifically, Japanese Patent Kokai No. 88109/88 discloses an antibacterial composition comprising a support of an oxide of Ti, Mg, Al or the like on which silver chloride is applied.
Recently, materials, industrial products and constructions have suffered from various damages by microorganisms such as molds and bacteria and other harmful organisms and many proposals have been made in an attempt to prevent such damages. One of them is the use of the above metallic copper fibers and besides various preventive means using antimicrobial properties of the above-mentioned metals have been extensively studied. For example, it has been attempted to support a metal component on solid powders such as zeolite by ion exchange reaction. (cf. Japanese Patent Kokai No. 133235/84).
However, the aforementioned silver chloride-supporting oxides and metal component-supporting zeolite powders have the following defects. That is, it is difficult to make them in the form of fine particles. The supported metal component readily falls off from the surface of particles. They are not sufficiently dispersible in media such as paint coating compositions, resin moldings, resin films, and coating compositions for paper processing. The amount must be increased in order to obtain sufficient antimicrobial effect and as a result, color tone of coated articles or molded articles applied therewith is damaged and desired color cannot be obtained. Thus, improvements thereof has been demanded. In case of appliances and high-grade household furnitures subjected to antimicrobial treatment which require beautiful coloring, the above improvement has been especially strongly desired.